1. Field of the Invention
The present invention relates to filter media, to methods of making filter media, and to filter elements made using the described filter media. More particularly, the present invention relates to accordion-pleated filter material in which adjacent filter strip sections are substantially parallel to one another.
2. Description of the Background Art
A number of different filter media are known for filtering fluids. Examples of some issued patents relating to filter materials, and to known fluid filter designs, include U.S. Pat. No. 2,019,186 to Kaiser, U.S. Pat. No. 2,732,951 to R. De Puiffe De Magondeau, U.S. Pat. No. 3,019,127 to Czerwonka et al., U.S. Pat. No. 3,971,373 to Braun, U.S. Pat. No. 4,537,812 to Elbers, U.S. Pat. No. 4,842,739 to Tang, U.S. Pat. No. 5,149,468 to Hershelman, U.S. Pat. No. 5,352,274 to Blakley, U.S. Pat. No. 5,810,898 to Miller, U.S. Pat. No. 6,113,784 to Stoyell et al., and U.S. Pat. No. 6,273,938 to Fanselow et al.
The assignee of the present invention has developed a new type of hollow xe2x80x98wickingxe2x80x99 fiber material that has been used for some filter applications. This material includes hollow spaces within the individual fibers, and this hollow space may be used to house a reactive or adsorbent material. Some issued patents relating to this wicking fiber, and to filters containing this type of fiber include U.S. Pat. Nos. 5,057,368, 5,704,966, 5,713,971, 5,744,236, 5,759,394, 5,891,221, 5,902,384, 5,951,744, 6,004,381, 6,048,614, 6,117,802, and 6,127,036. Other patents using this fiber technology are pending.
Although the known filter media are usable for their intended purposes, a need still exists in the art for an improved filter material which is minimally restrictive of a fluid being filtered.
It would be advantageous if such a filter material included some activated carbon to aid in the effectiveness thereof.
The present invention provides a filter material, a method of making the filter material, and a filter element incorporating the filter material.
The filter material of the present invention is useful for filtering fluids, and includes at least one filter pad, made using a thin sheet of nonwoven fiber material, which is folded many times back and forth, as further described herein.
The filter pad is a lightweight, elastically resilient pad which is generally compressible and deformable, but which tends to spring back to its original shape after compression, distortion or bending. In one particular embodiment of the invention, the filter pad is roughly box-shaped, including top, bottom, front, rear, and two opposed side surfaces.
The filter pad is formed from at least one thin, substantially flat fibrous sheet, which has been accordion-pleated, compressed into a unit made up of a multiplicity of interconnected, substantially parallel thin strips, and heated to substantially fix the strips in substantially parallel relation. Optionally, carbon particles may be applied to a portion of the fiber sheet before the folding operation thereon. The thin filter strips making up the filter material are oriented substantially parallel to one another, within the filter pad. Preferably, the finished filter material includes between 50-300 layers of filter strips per inch.
In one particular embodiment of the invention, two thin fibrous mats are placed in parallel with a layer of carbon particles sandwiched therebetween. The resulting layered material is then accordion-folded as previously described, and the double layer of fibrous material helps to trap the carbon and hold it in place.
The filter pad is adapted to filter fluid material passing inwardly through the front surface and outwardly through the rear surface thereof, the filtrate flowing directionally such that some of the filtrate passes between adjacent filter strips thereof, and in a direction which is generally parallel to the filter strips.
Preferably, in the practice of the present invention, the filter strips within the filter pad are very closely spaced next to, or are in side-to-side contact with one another, and are substantially parallel, as noted.
Optionally, in a preferred embodiment of the invention, the material of the filter pad may further include carbon particles held between selected filter strips. Where used, the carbon particles are preferably applied as a coating on at least one surface of the flat starting material, before it is pleated. The carbon may be sprayed on as a powder, and may be conventionally sprayed, or may be electrostatically applied. Then, after the carbon has been applied to the flat sheet, it is accordion-pleated, thereby trapping the carbon between adjacent strip surfaces.
Another optional feature of the filter material hereof is that selected fibers, of the nonwoven fiber starting material, may be hollow fibers. The portion of hollow fibers in the material, where used, is preferred to be between 5 percent and 80 percent, by weight, of the total fibers. Each of these hollow fibers has a hollow internal cavity formed therein, and has at least one extended slot formed therein, parallel to the longitudinal axis thereof. The hollow internal cavity of the fiber is able to communicate with the outer fiber surface by way of this extended slot.
In a particularly preferred version of the hollow fibers, each of the fibers includes a central stem and a plurality of substantially T-shaped lobes extending radially outwardly from the stem. Where this type of fiber is used, a number of lobes between two and five is preferred.
An added benefit of using this type of hollow fiber in the filter material, is that some of the hollow fibers may have fine carbon particles trapped inside the hollow internal cavities thereof. This additional carbon material, within the fibers, provides extra effectiveness and longevity to the filter material hereof.
It will therefore be understood that the filter material hereof may include two separate and distinct phases of activated carbon therein. The first phase of carbon is made up of the layer of carbon particles which may be trapped between adjacent strips of the filter pad. The second phase of carbon consists of the fine carbon particles which may be disposed within the internal cavities of the hollow fibers.
A filter element may be formed from the filter material according to the invention by attaching a circumferential edge frame to one or more filter bodies, substantially surrounding the top, bottom, and side surfaces thereof. The circumferential edge frame, where used, is formed from a different material than the filter pad. In a first orientation of the filter material in a filter element, the edge frame is placed around the filter pad such that when the filter element is used, at least some of the material to be filtered passes between adjacent filter strips thereof. In a second orientation of the filter material in a filter element, the edge frame is placed around the filter pad such that when the filter element is used, the material to be filtered passes through the interconnected filter strips thereof.
The present invention also contemplates a method of making a filter material. In practicing the method hereof, activated carbon is applied to at least one side of a thin sheet of fiber material comprising a plurality of nonwoven fibers.
After the carbon has been applied thereto, the sheet is then folded back and forth on itself many times, to form a multiplicity of interconnected filter strips.
The next step in the method hereof is compressing the folded sheet of fibrous material until the filter strips are oriented substantially parallel to one another, and the carbon is mechanically held between adjacent filter strips.
The next step in the method involves heating the folded and compressed sheet to fix and retain the substantially parallel orientation of the filter strips therein, forming the filter pad.
Optionally, the method may include an additional step of placing one or more filter pads into a frame, to form filter element adapted to directionally filter fluid therethrough, in a manner such that some of the fluid to be filtered passes between adjacent interconnected, substantially parallel filter strips.
Accordingly, it is an object of the present invention to provide an improved filter material.
It is another object of the present invention to provide a method of making the novel filter material.
It is a further object of the present invention to provide a filter element made using the improved filter material.
For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts.